Removable stem for raise bits

ABSTRACT

A raise bit for enlarging a pilot hole into a larger diameter hole by disintegrating the earth formations surrounding the pilot hole includes a removable drive stem. The removable drive stem allows the raise bit to be transported through small drifts and helps extend the useful lifetime of the raise bit. The raise bit may be assembled without weakening the highly-stressed, heattreated drive stem by welding. The raise bit body includes a multiplicity of rolling cutters for contacting and disintegrating the earth formations surrounding the pilot hole. The raise bit body includes a fixed collar with a truncated conical inside surface. A two-piece, split, removable collar with an inside surface that matches the outside surface of the drive stem and a conical outer surface that matches the inside surface of the fixed collar is positioned around the drive stem. A flange at the end of the drive stem allows the split collar to be drawn up into the fixed collar thereby developing frictional forces between the mating surfaces of the fixed collar, the split collar, and the drive stem. A preload is induced into the system to insure proper torque transmittal at low bit loads.

United States Patent [191 Dyer et al.

[ REMOVABLE STEM FOR RAISE BITS [75] Inventors: Norman Dean Dyer, Plano;Howard Earl Mitchell, Duncanville, both of Tex.

[73] Assignee: Dresser Industries, Inc., Dallas, Tex.

[22] Filed: Sept. 16, 1974 [21] Appl. No.: 506,667

[52] US. Cl. 175/53; 175/334; 285/323; 403/371 [51] Int. Cl. E21C 23/00;E21B 9/24 [58] Field of Search 175/53, 325, 334, 344, 175/391; 403/370,371; 285/421, 323

[56] References Cited UNITED STATES PATENTS 827,346 7/1906 Bubb....403/371 2,556,151 6/1951 Bremer.... 403/370 X 2,570,604 10/1951Siegerist 403/371 X 2,819,099 1/1958 Rittle 285/323 X 3,231,029 1/1966Winberg 175/53 3,659,659 5/1972 Lichte 175/334 X 3,675,729 7/1972Neilson 175/53 X 3,738,691 6/1973 Firth 403/370 3,805,901 4/1974 Coski175/53 NOV. 4, 1975 Primary Examiner-David H. Brown Attorney, Agent, orFirm-Eddie E. Scott ABSTRACT A raise bit for enlarging a pilot hole intoa larger diameter hole by disintegrating the earth formationssurrounding the pilot hole includes a removable drive stem. Theremovable drive stem allows the raise bit to be transported throughsmall drifts and helps extend the useful lifetime of the raise bit. Theraise bit may be assembled without weakening the highly-stressed,heat-treated drive stem by welding. The raise bit body includes amultiplicity of rolling cutters for contacting and disintegrating theearth formations surrounding the pilot hole. The raise bit body includesa fixed collar with a truncated conical inside surface. A two piece,split, removable collar with an inside surface that matches the outsidesurface of the drive stem and a conical outer surface that matches theinside surface of the fixed collar is positioned around the drive stem.A flange at the end of the drive stem allows the split collar to bedrawn up into the fixed collar thereby developing frictional forcesbetween the mating surfaces of the fixed collar, the split collar, andthe drive stem. A preload is induced into the system to insure propertorque transmittal at low bit loads.

8 Claims, 3 Drawing Figures U.S. Patent .Nov.4, 1975 Sheet 1 of33,917,009

U.S. Patent Nov; 4, 1975 Sheet 3 of3 3,917,009

REMOVABLE STEM FOR RAISE BITS BACKGROUND OF THE INVENTION The presentinvention relates to the art of earth boring and more particularly to araise bit for enlarging a pilot hole into a larger diameter hole bydisintegrating the earth formations surrounding the pilot hole.

A relatively large diameter hole may be provided between a firstlocation and a second location in a mine by an operation commonlyreferred to as raise drilling. A raise drilling operation begins bydrilling a small diameter pilot hole through the earth from the firstlocation to an opening at the second location using a small diameterpilot bit. After the pilot hole is completed, the pilot bit is removedfrom the drill column and a large diameter raise bit attached. The raisebit is rotated and drawn along the pilot hole thereby enlarging thepilot hole to the desired size.

On many occasions, the small diameter pilot hole extends to an areaaccessible only through a small drift or passage. The removable drivestem of the present invention provides a raise bit with a low profilethereby allowing the raise bit to be transported through small drifts orpassages. For example, a 72-inch diameter raise bit incorporating thepresent invention may be transported through a drift having a 30-inchheight whereas a 72-inch diameter raise bit without the removable stemrequires a drift with at least a 52-inch height.

During a raise drilling operation a tremendous amount of wear and stressis imposed upon the raise bit. Generally the pilot hole tends to wanderthereby resulting in a series of curves over the length of the pilothole. As the raise bit is drawn along the pilot hole the drillinggeometry changes. This results in a tremendous amount of stress beingtransmitted to the raise bit when it is being drawn through the curves.The outside radius of the raise bit may be many times greater than theradius of the pilothole, therefore, the moment developed is great. Whenresistance is encountered by cutters located on the outer radius of theraise bit as when drilling along the curve, it causes increased stresson the raise bit. lt can be appreciated that any changes in formationsencountered during the raise drilling operation complicates theabove-mentioned conditions and adds to the drilling difficulties.

The tremendous stress and wear encountered during the raise drillingoperation causes some elements of the raise bit to-wear out much fasterthan others, notably, the cutters and the drive stem. The bit of thepresent invention allows the elements that have a relatively shortlifetime to be replaced thereby extending the lifetime of the bit andreducing cost. The drive stem is removable, and therefore, replaceableas are the individual cutters. This allows the elements that receive thegreatest stress and wear to be readily replaced. The relatively shortlifetime of the individual cutters results from their nearly constantcontact with the formations and their constant exposure to wear andabuse. The drive stem also contacts the formations and receives a greatdeal of wear and abuse. The drive stem absorbs a large amount of stresssince it is the single link between the drill column and the body of thebit. All energy from the rotary equipment is transmitted to the raisebit through the drive stem.

The drive stem is very often subject to failure prior to failure of thebody of the raise bit. It is, therefore, desirable to be able to easilyand quickly remove the stem from the raise bit and replace it with a newdrive stem. The stem is generally constructed ofa' high-strength,heat-treated material and would be weakened by welding. It is,therefore, desirable to be able to attach and remove the stem from theraise bit body without welding. From the foregoing, it will beappreciated that the stem must be constructed of material that willstand up under the harsh conditions encountered. Such material isexpensive and any reduction in the amount of this material required is acost savings. The bit of the present invention allows the stem to bemanufactured from high-strength material, whereas the body may includelower strength and, therefore, less expensive materials.

The stem or a stabilizer section on the stem should be nearly the sizeof the pilot hole during the'raise drilling operation to insure a smoothdrilling operation. In order to use the same bit body in pilot holes ofdifferent sizes, it is desirable to be able to remove the stem from theraise bit body and replace it with an appropriately sized stem. The stemshould be easy to remove and replace using simple hand tools. Thisallows the stem to be replaced in the field under adverse conditions.

DESCRIPTION OF PRIOR ART A general description of a raise drillingoperation is presented in us. Pat. No. 3,220,494 to R. E. Cannon et al,patented Nov. 30, 1965. In the system disclosed in this patent, a pilothole is enlarged to the desired raise body of the bit includes a seriesof plates separated by a series of hollow support elements.

Raise bits manufactured by The Robbins Company, 650 South Orcas Street,Seattle, Washington 98108, include a stem that may be replaced bydisconnecting taper collets on the top of the body that mate with thetapered section on the stem and disconnecting a bolt with a splittapered bushing that extends through the lower end of the stem.

SUMMARY OF THE INVENTION The present invention provides a raise bit forenlarging a pilot hole into a large diameter hole by disintegrating theearth formations surrounding the pilot hole. The body of the raise bitincludes a multiplicity of rolling cutters for contacting anddisintegrating the earth formations surrounding the pilot hole. A collarwith a truncated conical inside surface is affixed to the raise bitbody. One end of the drive stern extends into the collar. A two-piece,split collar with an inside surface that matches the outer surface ofthe stem and a conical outer surface that matches the inside surface ofthe collar is positioned around the lower end of the drive stem. Thedrive stem and split collar are then drawn up into the collar.Frictional forces are developed between the mating surfaces of thecollar, the split collar, and the drive stem thereby preventingrotational, radial, and axial movement of the drive stem with respect tothe raise bit body. v i

The drive stem of the present invention may be removed and a new drivestern inserted in its place. The

3 raise bit of the present invention may be transported through smalldrifts or passages by removingthe drive stem from the raise bit body.The drive stern may then be reattached and the raise bit is ready foroperation. The high-strength, heat-treated stem is not weakened bywelding. The raise bit body may be constructed of materials that areless expensive than the materials that make up the drive stem. Differentsized drive stems may be attached to the raise bit body to allow theraise bit to be used in pilot holes of different sizes. The removal ofthe stern and replacement with a new stem may be accomplished in thefield under adverse conditions with simple hand tools. Zero clearance isprovided between the stem, the split collar, and the collar. Thisinsures a rigid connection between the drive stem and the raise bitbody. The drive stem of the present invention may be easily removed anda new stem put in place without removing the cutter saddles adjacent thestem. The above and other features and advantages of the presentinvention will become apparent from a consideration of the followingdetailed description of the invention when taken in conjunction with thedrawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a side view of a bitconstructed in accordance with the present invention.

FIG. 2 is an exploded view ofa portion of the raise bit shown in FIG. 1.

FIG. 3 shows the location of the elements shown in FIG. 2 when theelements are assembled.

DETAILED DESCRIPTION OF THE INVENTION Referring now to FIG. 1, a sideview of a raise bit constructed in accordance with the present inventionand generally designated by the reference number is shown. The raise bit10 includes a raise bit body 11 or cutter stage body and a drive stem12. The upper portion of the drive stem 12 is enlarged to form astabilizer section 13. The raise bit 10 is adapted to be connected to arotary drill column by a threaded connection 14. A multiplicity ofrolling cutters 15 are mounted in a corresponding multiplicity ofsaddles 16. The saddles 16 extend from the raise bit body 11.

The-raise bit 10 is used in a raise drilling operation to provide arelatively large diameter hole from a first mine level to a second minelevel. The raise drilling operation begins by drilling a small diameterpilot hole through the earth from a first location to an opening at asecond location using a small diameter pilot bit. After the pilot holeis completed, the pilot bit is removed from the drill column and theraise bit 10 is attached to the drill column. The raise bit 10 isrotated and drawn along the pilot hole thereby enlarging the pilot holeto the desired size.

Referring now to FIG. 2, an exploded view of a portion of the stem 12and raise bit body 11 is shown. A cylindrical collar 17 is affixed tothe raise bit body 11. The collar 17 has a truncated conical insidesurface 24. The apex of the conical surface 24 intersects the center ofrotation of the raise bit. The lower end of the drive stem 12 extendsthrough the collar 17. A two-piece, split, removable collar consistingof sections 18 and 19 is positioned around the drive stem 12. Thesection 18 includes a surface 25 that forms a portion of a conical outersurface that matches the conical inner surface 24 of collar 17. Thesection 19includes a surface 26 that forms a portion of theaforementioned conical outer surface that matches the conical innersurface 24 of 4 collar 17. The section 18 includes a surface 27 thatforms a portion of a cylindrical inner surface that matches thecylindrical outer surface 29 of drive stem 12. The section 19 includes asurface 28 that forms a portion of the aforementioned cylindrical outersurface 29 of drive stem 12. A flange 20 extends from the lower end ofthe drive stem 12. A cap 21 is positioned below the flange 20 and a pairof bolts 22 and 23 are positioned to extend through holes 30 and 31respectively in the cap 21 and engage threaded recesses 32 and 33respectively in the collar 17.

Referring now to FIG. 3, the elements of FIG. 2 are shown in theirassembled position. The sections 18 and 19 of the split collar arepositioned around the lower end of the drive stem 12. The stem 12 andthe sections 18 and 19 are then drawn up into the collar 17. The stem 12is initially prevented from pulling through the collar 17 by the flange20 extending from the lower end of stem 12. The flange 20 also exertsforce on the sections 18 and 19 of the split collar forcing it eventighter against the collar 17. The matching conical surfaces on thecollar 17 and the sections 18 and 19 of the split collar force thesections 18 and 19 against the outer surface of the stem 12. A loadapplied to the raise bit increases the aforementioned forces. Frictionalforces developed between the mating surfaces of the collar 17 and thesections 18 and 19, and the drive stem 12 prevent rotational, radial,and axial movement of the drive stem 12 with respect to the raise bitbody 11. A preload is induced into the system to insure proper torquetransmittal at low bit loads by the cap 21 and bolts 22 and 23. Whenbolts 22 and 23 are tightened, they urge the cap 21 against the flange20 and the sections 18 and 19 upward in the collar 17.

The structural details of a raise bit constructed in accordance with thepresent invention having been described, a raise drilling operation willnow be considered using the bit shown in FIGS. 1, 2, and 3. The raisedrilling operation begins by drilling a small diameter pilot holethrough the earth from a first location to an opening at a secondlocation using a small diameter pilot bit. After the pilot hole iscompleted, the pilot bit is removed from the drill column and the raisebit 10 is attached to the drill column. The raise bit is rotated anddrawn along the pilot hole, thereby enlarging the pilot hole to thedesired size. The collar 17 and sections 18 and 19 of the split collarprovide a rigid connection between the drive stem 12 and the raise bitbody 11.

The raise bit may be transportedthrough small drifts or passages byremoving the drive stem 12 and transporting the drive stem 12 and theraise bit body 11 through the small drifts or passages separately. Thebolts 22 and 23 are removed, thereby disconnecting the cap 21 from thecollar 17. The drive stem 12 and the sections 18 and 19 of the splitcollar are moved downward thereby disengaging the sections 18 and 19 ofthe split collar from the collar 17. With the split collar removed, thedrive stem 12 may be removed from the raise bit body 11. The separateelements of the raise bit 10 may then be transported separately throughthe small drift or passage. When the raise bit 10 is to be connected tothe drill column, the drive stem 12 is inserted through the collar 17.The sections 18 and 19 of the split collar are positioned around thelower end of the drive stem 12 and the drive stem 12 and the splitcollar are moved upward into the collar 17. The cap 21 is positioned incontact with the flange 20 and bolts 22 and 23 are engaged with thethreaded recesses 32 and 33 respectively. Tightening of the bolts 22 and23 imposes a preload on the system. The raise bit is again ready foroperation.

Should the drive stem 12 experience failure prior to failure of theraise bit body 11, the drive stem may be removed from the raise bit body11 and a new drive stem inserted in its place. The bolts 22 and 23 areremoved thereby disconnecting the cap 21 from the collar 17. The drivestem 12 and sections 18 and 19 of the split collar are moved downwardthereby disconnecting the drive stem 12 from the raise bit body 11. Thedrive stem 12 is removed and the new drive stem inserted through thecollar 17. The sections 18 and 19 of the split collar are positionedaround the new drive stem and the new drive stern and the sections 18and 19 of the split collar are moved upward into the collar 17. The cap21 is positioned in contact with the flange on the end of the new drivestern and bolts 22 and 23 are engaged in the threaded recesses 32 and33. Tightening of the bolts 22 and 23 imposes a preload on the systemand the raise bit is ready for operation.

The embodiment of the invention in which an exclusive property orprivilege is claimed are defined as follows:

l. A bit for enlarging a pilot hole into a larger diameter hole bydisintegrating earth formations surrounding the pilot hole, comprising:

a drive stern having an upper end for projecting into said pilot hole;

a main bit body including a multiplicity of cutters for contacting anddisintegrating earth formations surrounding the pilot hole;

a central opening in said main bit body substantially surrounding saiddrive stern, said central opening having a conical inner surface thattapers inward toward said drive stem in the direction of said upper endof said drive stem;

and means around said drive stern having a tapered outer surface thattapers inward toward said drive stem in the direction of said upper endof said drive stem and engages said conical inner surface for retainingsaid drive stem in said central opening and connecting said drive stemto said main bit body.

2. The bit of claim 1 including a flange projecting from said drive stemfor contacting said means around said drive stem.

3. The bit of claim 2 wherein said drive stem has a lower end, said bitincluding a cap that fits over said lower end of said drive stem andbolt means for forcing said cap against said lower end of said drivestem.

4. A raise bit for enlarging a pilot hole into a larger diameter hole bydisintegrating earth formations surrounding the pilot hole, comprising:

a cutter stage body, said cutter stage body having an upper portion anda lower portion;

a multiplicity of saddles mounted on said upper portion of said cutterstage body;

a multiplicity of rolling cutters positioned in said saddies;

a central opening in said cutter stage body, said central opening havinga conical inner surface tapering toward said upper portion of saidcutter stage body;

a drive stem positioned in said central opening;

retaining element means around said drive stem for retaining said drivestem in said central opening, said retaining element means having anouter surface adapted to mate with said conical inner surface; and

means for urging said retaining element means into said central opening.

5. The raise bit of claim 4 wherein said retaining element means is atwo-piece collar with a conical outer surface tapering toward said upperportion of said cutter stage body.

6. A bit for enlarging a pilot hole into a larger diameter hole bydisintegrating earth formations surrounding the pilot hole, comprising:

a drive stem having an upper end for projecting into said pilot hole;

a main bit body including a multiplicity of cutters for contacting anddisintegrating earth formations surrounding the pilot hole;

a collar positioned around said drive stem connected to said main bitbody, said collar having a conical inner surface that tapers inwardtoward said drive stem in the direction of said upper end;

a retaining element having a conical outer surface that matches saidconical inner surface adapted to be positioned around said drive stem;

a flange on the end of said drive stem for urging said retaining elementinto said collar; and

cap means for contacting said flange and urging said retaining elementinto said collar.

7. A raise bit for enlarging a pilot hole into a larger diameter hole bydisintegrating earth formations surrounding the pilot hole, comprising:

a drive stem having an upper end for projecting into said pilot hole anda lower end;

a cutter stage body;

a multiplicity of saddles mounted on said cutter stage body;

a multiplicity of rolling cutters positioned in said saddles;

a collar positioned around the lower end of said drive stem andconnected to said cutter stage body, said collar having an inner conicalsurface that tapers inward toward said drive stern in the direction ofsaid upper end; and

a retaining element means positioned between said collar and said drivestem, said retaining element means having a tapered outer surfaceadapted to mate with said conical inner surface.

8. The raise bit of claim 7 including a flange projecting from saiddrive stem and a cap means positioned over said flange for urging saidtapered surface into contact with said conical inner surface.

1. A bit for enlarging a pilot hole into a larger diameter hole bydisintegrating earth formations surrounding the pilot hole, comprising:a drive stem having an upper end for projecting into said pilot hole; amain bit body including a multiplicity of cutters for contacting anddisintegrating earth formations surrounding the pilot hole; a centralopening in said main bit body substantially surrounding said drive stem,said central opening having a conical inner surface that tapers inwardtoward said drive stem in the direction of said upper end of said drivestem; and means around said drive stem having a tapered outer surfacethat tapers inward toward said drive stem in the direction of said upperend of said drive stem and engages said conical inner surface forretaining said drive stem in said central opening and connecting saiddrive stem to said main bit body.
 2. The bit of claim 1 including aflange projecting from said drive stem for contacting said means aroundsaid drive stem.
 3. The bit of claim 2 wherein said drive stem has alower end, said bit including a cap that fits over said lower end ofsaid drive stem and bolt means for forcing said cap against said lowerend of said drive stem.
 4. A raise bit for enlarging a pilot hole into alarger diameter hole by disintegrating earth formations surrounding thepilot hole, comprising: a cutter stage body, said cutter stage bodyhaving an upper portion and a lower portion; a multiplicity of saddlesmounted on said upper portion of said cutter stage body; a multiplicityof rolling cutters positioned in said saddles; a central opening in saidcutter stage body, said central opening having a conical inner surfacetapering toward said upper portion of said cutter stage body; a drivestem positioned in said central opening; retaining element means aroundsaid drive stem for retaining said drive stem in said central opening,said retaining element means having an outer surface adapted to matewith said conical inner surface; and means for urging said retainingelement means into said central opening.
 5. The raise bit of claim 4wherein said retaining element means is a two-piece collar with aconical outer surface tapering toward said upper portion of said cutterstage body.
 6. A bit for enlarging a pilot hole into a larger diameterhole by disintegrating earth formations surrounding the pilot hole,comprising: a drive stem having an upper end for projecting into saidpilot hole; a main bit body including a multiplicity of cutters forcontacting and disintegrating earth formations surrounDing the pilothole; a collar positioned around said drive stem connected to said mainbit body, said collar having a conical inner surface that tapers inwardtoward said drive stem in the direction of said upper end; a retainingelement having a conical outer surface that matches said conical innersurface adapted to be positioned around said drive stem; a flange on theend of said drive stem for urging said retaining element into saidcollar; and cap means for contacting said flange and urging saidretaining element into said collar.
 7. A raise bit for enlarging a pilothole into a larger diameter hole by disintegrating earth formationssurrounding the pilot hole, comprising: a drive stem having an upper endfor projecting into said pilot hole and a lower end; a cutter stagebody; a multiplicity of saddles mounted on said cutter stage body; amultiplicity of rolling cutters positioned in said saddles; a collarpositioned around the lower end of said drive stem and connected to saidcutter stage body, said collar having an inner conical surface thattapers inward toward said drive stem in the direction of said upper end;and a retaining element means positioned between said collar and saiddrive stem, said retaining element means having a tapered outer surfaceadapted to mate with said conical inner surface.
 8. The raise bit ofclaim 7 including a flange projecting from said drive stem and a capmeans positioned over said flange for urging said tapered surface intocontact with said conical inner surface.